Known techniques regarding containers comprising a pulp molded article having a resin layer provided thereon include, for example, the one disclosed in JP-A-10-46500. The publication discloses a method of obtaining a shallow molded tray comprising spraying an aqueous polymer solution onto the inner side of a pulp layer with a prescribed water content either before dewatering or after room-temperature dewatering and drying the pulp layer by means of a hot press, etc.
According to this method, however, because the sprayed aqueous polymer solution penetrates into the pulp layer, a large quantity of the aqueous polymer solution is required to form a layer of sufficient thickness for manifesting waterproofness and moistureproofness, and a long drying time is needed, resulting in an increased production cost. Besides, the aqueous polymer solution having penetrated into the pulp layer acts as a binder for pulp fibers to impair disintegrability of pulp fibers, which makes recycling difficult.
Where a thick resin layer is formed on both the inner and the outer surfaces of a pulp molded article in an attempt to enhance barrier properties against gas or liquid, blisters develop between the molded article and the resin layers, resulting in not only reduced barrier properties but impaired appearance. Blisters are a phenomenon that, where a coating is applied to one side of a molded article previously having a resin layer provided on the other side, the solvent volatilizing from the coating on drying is unable to find the way out, causing the resin layer to lift from the molded article surface.
Additionally, where a thick resin layer is formed through a single coating operation, the applied coating sags or runs, resulting in non-uniformity of various properties of the resin layer after drying. It is conceivable to repeatedly applying a coating thinly to obtain desired performance, but such involves an increased number of production steps, which reduces production efficiency and is economically disadvantageous.
Another technique known for improving performance of a pulp molded article is providing a part of a pulp molded article with a molded piece made of a synthetic resin. For example, JP-A-6-278160 teaches injection molding the same resinous component as used in a pulp molded article into a molded piece integral with the pulp molded article. According to the technique disclosed, since the molded piece and the molded article are integral with each other, it is bard to separate them before putting out for separated garbage collection. In order to exclude necessity of separation, it is desirable to make up a product solely of a pulp molded article without using such a molded piece of different material. In this case, however, particularly for use as a container with lid or cap, shape precision necessary for assuring a desired tight fit or durability withstanding repeated use would not be sufficiently secured.